This poem is from the proverbial distichs of Georgius Carolides (1569-1612), which you can read online at the University of Mannheim.
Ne Bos in Lingua
Munere corrumpi taceas ut vera caveto,
Gestare in lingua ne videare bovem.
Source: Georgius Carolides (1569-1612), Farrago, 2.57. Meter: Elegiac. The "ox" in this poem refers to a coin stamped with an ox (as in the coin below), so to "have an ox on your tongue" was a turn of phrase indicating that someone had accepted a bribe to stay silent.
Be careful (caveto) not to be bribed by a gift (corrumpi munere) to keep silent about the truth (ut taceas vera): you don't want to seem (ne videare) to have an ox (gestare bove) on your tongue (in lingua).
The vocabulary is keyed to the DCC Latin Vocabulary list. There is only one word in this poem that is not on the DCC list:
gestō, gestāre: carry, bear, wear
bōs bovis m.: ox; gen. pl. boum
caveō cavēre cāvī cautum: be on guard, beware
corrumpō -rumpere -rūpī -ruptum: break up, destroy, ruin
in: in, on (+ abl.); into, onto (+ acc)
lingua -ae f.: tongue; language
mūnus mūneris n.: gift, offering
nē: lest, that not
taceō -ēre -uī -itum: be silent; tacitus -a -um, silent
ut, uti: as (+ indic.); so that, with the result that (+ subj.)
vērus -a -um: true; vērē, truly
videō vidēre vīdī vīsum: see